Various methods for rotary position sensing are known, for example, capacitive and inductive position sensors are known. But many of the sensors employed are contact sensors in which the mechanical movement of one member relative to another is traced by mechanical displacement of electrical conductors in order to electrically represent the change in position. Such sensors are subject to mechanical wear that can substantially affect the efficiency and longevity of the electrical conductors and other moving components. Moreover, inherent electrical noise in the output signal can limit the resolution to a relatively large increment of angular displacement.
An alternative form of sensors are generally referred to as non-contact sensors, but such sensors are not always adaptable for certain types of rotary position sensing. For example, conventional capacitive non-contact sensors often rely on changes in the absolute capacitance between two electrodes to generate the control signal. But the absolute value of capacitance can be affected by environmental conditions such as the variations in temperature, moisture, debris, vibration and other factors to which a sensor might be subjected. Other types of non-contact sensors such as Hall Effect transducers increase the cost or complexity of the sensing assembly and signal processing. Thus, position sensors needed for precise position detecting applications typically either require a costly assembly of components or a great deal of calibration to obtain the accuracy required.
Furthermore, many sensors can, over time, lose accuracy due to play of components or are temperature sensitive, thus losing the precision required for the particular application.
Another example of non-contact sensors are magnetic sensors. But these sensors can also end up being expensive to construct and assure that the precision of the magnetic sensing is not affected by its surroundings. Moreover, these types of sensor assemblies may affect other adjacent sensors or components due to the magnetic field produced by this particular magnetic sensor assembly.
Thus, it is desirable for particular high precision positional sensing needs to employ a non-contact sensor assembly that will maintain its accuracy over time for various temperature conditions and will not interfere with or be interfered with by components that may be adjacent to the sensor. Also, preferably, this sensor will accomplish these objectives with minimal cost needed to produce and operate the sensor.